席雅允, 刘娟红, 程立年. 铁尾矿粉混凝土在荷载与硫酸盐干湿循环耦合作用下的性能劣化机理[J]. 工程科学学报, 2024, 46(8): 1358-1369. DOI: 10.13374/j.issn2095-9389.2023.09.13.006
引用本文: 席雅允, 刘娟红, 程立年. 铁尾矿粉混凝土在荷载与硫酸盐干湿循环耦合作用下的性能劣化机理[J]. 工程科学学报, 2024, 46(8): 1358-1369. DOI: 10.13374/j.issn2095-9389.2023.09.13.006
XI Yayun, LIU Juanhong, CHENG Linian. Mechanism of performance deterioration of iron tailing powder concrete under the coupling effect of load and sulfate dry–wet cycle[J]. Chinese Journal of Engineering, 2024, 46(8): 1358-1369. DOI: 10.13374/j.issn2095-9389.2023.09.13.006
Citation: XI Yayun, LIU Juanhong, CHENG Linian. Mechanism of performance deterioration of iron tailing powder concrete under the coupling effect of load and sulfate dry–wet cycle[J]. Chinese Journal of Engineering, 2024, 46(8): 1358-1369. DOI: 10.13374/j.issn2095-9389.2023.09.13.006

铁尾矿粉混凝土在荷载与硫酸盐干湿循环耦合作用下的性能劣化机理

Mechanism of performance deterioration of iron tailing powder concrete under the coupling effect of load and sulfate dry–wet cycle

  • 摘要: 铁尾矿粉作为矿物掺合料应用于混凝土有助于固废高值化利用和节能减排,而关于铁尾矿粉混凝土抗硫酸盐侵蚀性能的研究,大多只考虑了单一条件或者加速条件环境,其在多种环境耦合下的劣化特征尚未得到探究. 本文将铁尾矿粉作为矿物掺合料应用于混凝土中,以相对动弹性模量、质量损失率为性能指标,研究荷载–硫酸盐干湿循环耦合作用下铁尾矿粉混凝土劣化过程,探究铁尾矿粉掺量和荷载率对铁尾矿粉混凝土内部劣化的影响,结合扫描电镜(SEM)、X-ray衍射分析(XRD)、压汞(MIP)等微观手段揭示铁尾矿粉混凝土在耦合作用下损伤劣化机理. 结果表明:适量铁尾矿粉的掺入有利于其与矿粉的协同水化作用,提高混凝土水化程度和基体密实度,减少硫酸根离子传输路径,提高混凝土抗硫酸盐侵蚀能力;荷载的施加使试块内部微裂纹宽度和数量增加,为硫酸根离子的进入提供更多渗透路径,加速铁尾矿粉混凝土损伤劣化过程;耦合作用使得铁尾矿粉混凝土内部损伤不断累积,在微观上表现为结构的疏松和裂缝的衍生扩展,在宏观上表现为力学性能的衰减和整体结构完整性的下降.

     

    Abstract: The application of iron tailing powder to concrete as a mineral admixture promotes high-value use of solid waste and energy saving and emission reduction. However, most studies on the durability of iron tailing powder concrete only consider single conditions or accelerated conditions, and its deterioration characteristics under multiple environmental coupling remain unexplored. In this paper, an iron tailing powder admixture is applied to concrete. The relative dynamic elastic modulus and mass loss rate are used as performance indexes to study the deterioration process of iron tailing powder concrete under load–wet–cycling–sulfate coupling and to explore the influence of iron tailing powder content and load rate on the internal deterioration of iron tailing powder concrete. Scanning electron microscopy, X-ray diffraction analysis, and mercury injection revealed the damage and deterioration mechanism of iron tail powder concrete under coupling action. The results show that the proper addition of iron tailings benefits the synergistic hydration between iron tailings and slag powder to achieve the synergistic and complementary effect and improve the hydration degree of concrete. As a composite admixture, the mixture of the two considerably impacts the performance of concrete. The degree of damage and deterioration of the iron tailing concrete decreases and then increases with increasing iron tailing content. The sulfate corrosion resistance of concrete is optimal when the dosage is 50%. Adding a proper amount of iron tailing powder improves the compactness of iron tailing powder concrete, reduces the transport path of sulfate ions, improves the tensile strength of concrete, delays the appearance of microcracks caused by expansion products, and thus improves the corrosion resistance of iron tailing powder concrete. Under the coupled action, the expansion stress of ettringite and gypsum and the crystallization pressure caused by sulfate continuously increase the internal cracks of iron tailing powder concrete. Load application increases the width and number of microcracks in the test block. When the load rate exceeds 40%, the load accelerates the elastic deformation of cracks, reduces the effective bearing area of concrete, reduces the bearing capacity, and destabilizes the internal structure. At the same time, continuous calcium dissolution formed more channels inside the concrete and provided favorable conditions for infiltration and erosion by sulfate ions. The repeated dry–wet cycle caused the internal damage of the concrete to accumulate repeatedly, and the specimen was destroyed after reaching the ultimate strength of the concrete.

     

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